Coops experiments with LED's, batteries, lights and lighting

[CoopsMinis]

OK guys, I thought I’d share this with you because there isnt much out there in terms of lighting ideas for modular, mobile wargaming terrain. The model railway guys have lots of stuff, but it’s all 12V DC via mains transformer and permanently wired into their dioramas. Lighting modular wargaming terrain presents some unique challenges. Everything has to be mobile and self contained, which means small, efficient and battery powered.

We’ve all seen the tea-light campfires and I dont know how you feel about them? But I think they look naff. Mainly because the base is an inch and a half high …so people create these mounds of filler and rubble with a fire on top, which usually runs at eye level to the minis. Doesnt work for me, I’d rather do without. But this is the 21st century, there has to be other ways of doing it right?

Fortunately, there are options. Lots of em as it happens. The problem is figuring out the right approach. For me, it has to be cheap, easy, functional, realistic and at the end of it, it has to actually add something to the atmosphere, or it’s all pointless. I dont want tea lights covered in goop.

So lets start with the selection of LED’s…
They come in a wide variety of shapes, sizes and colours. You can get big ones, huger ones, pico ones, strip lights and so on. Most of em are a bit specialist and for our purposes, 99% of what we want will be either 3mm or 5mm standard. That refers to the diameter of the bulb. The other values we need to know, is what voltage they run on and how much current they consume. In terms of current, almost all of em are 20 milliamp (20mA sometimes written as 0.020 Amps). A 20 mA LED is perfect for us, for reasons I’ll come to in a bit. This shouldn’t be taken for granted though. It’s an important value and if you see LED’s for sale and they dont tell you what current they use, move on. There is no shortage of people selling them and they are cheap as chips.

The voltage is also important. Most white LED’s are 3 volts, but coloured LED’s are usually less …usually 1.8-2.2 volts. This is also an important value, because in most cases, we will be powering them with 3 volts from our battery. If our LED runs on 3 volts and our battery is 3 volts, then we can direct drive the LED. This means running the LED directly from the battery without any additional electronics and without the fear of our LED getting over-volted, overheating, burning out, excessive battery drain and so on. Fortunately, most LED’s are very voltage tolerant and can be run out of spec (within reason) without much of a problem. Generally, you can direct drive a 2 volt LED from a 3 volt battery, it’ll just run a bit brighter and a bit hotter than it should …and it’ll probably have a reduced lifespan.

More about LED’s later, but for now I’ll just say I’ve been experimenting with some different types. Different colours, some flickering and so on. I ordered quite a few and soldered them onto little bits of stripboard. I know I said you dont need additional electronics, but I wanted to test these running perfectly in spec, so I made sure the voltage was balanced by a matched resistor just so I know how they should perform…

In practice I would just wire them straight to the battery.

On the point of batteries…

I’ve looked at a few options and it’ll be no surprise that CR2032 coin cells is the way to go. They have a nominal 3 volts, they usually have a capacity of around 220 to 240 mAh and are at their optimal when the applications have a low current draw of around 20 mA. BTW, with coin cells, the numbers refer to the diameter and the height of the battery. So a 2032 cell is 20mm in diameter and 3.2mm high. A 2016 cell, is the same diameter and half the height …and so on.

So 2032’s are pretty much the perfect size, they are reliable, long lasting and suit the application …they are also cheap. I found a seller on Amazon selling 100 for £12.80 …that’s 12.8p each. Now consider your 20mA LED can run for a theoretical 12 hours on a 240 mAh battery and you have a running cost of 1.06 pence per hour (per LED). You can have a table with 20 LED’s and run them all for a 4 hour session and it would cost you 80p. I think that is pretty cheap.

There are other options, obviously. If you have the space inside your model thern rechargeable AA’s or AAA’s are the way to go. They are the cheapest of all, but they are comparatively bulky and unsightly.

On battery packs and switches, I think I have found the perfect off-the-shelf solution. Now dont laugh, but the solution comes from the world of kids crafts and girly textiles. There is something called -e-tectiles ,basically people sew LEDS and electronics into clothing using conductive thread. Well there is a company called Lilypad which has started doing components for e-textiles off the shelf. But because they are designed to be hidden in clothing, they are ultra low profile …which is very useful. Here is their 2032 switched battery pack…

and the reverse is nice and flat for sticking onto surfaces and such…

Nice logo eh? That’s all for now, but I’ll keep you updated with my experiments. Here’s a quick shot of a prototype I’m working on…

If it works out it’ll be a flickering yellow LED tilley lamp powered by a cr2032 in a lilypad.

I’d love to hear what solutions you guys have come up with for lighting? Do you think it’s worthwhile or a fad?

Cheers, Coop.

[Info_Overload]

I did have a discussion with a mate of mine about LEDs last year, but I’ve never done anything with it. I think it could add extra oomph to terrain if it’s used well.

I’m going to be following this thread with a lot of interest, thanks

[Alaiteir]

This is a brilliant guide, thanks for putting it together! The idea of using an e-textile switch seems brilliant for getting it to be low profile

[CoopsMinis]

@Alaiteir

The idea of using an e-textile switch seems brilliant for getting it to be low profile

Yeah, that’s key really. The Lilypad is 28mm in diameter, which is quite large. There are other battery holders that have a smaller diameter. But crucially, it sits only about 6mm high and has a completely flat back. Others are typically 2 or 3mm higher and have little solder nibs which act as a standoff on surfaces.

Imagine an LED soldered directly onto the contacts of the Lilypad and then bent 90 degrees downward? A perfect ceiling light. The Lilypad could be stuck onto the ceiling of any building with a bit of double sided tape. You’ll never see the Lilypad because you would have to be looking up into the building from outside and it’s so low profile it wont be visible through the windows. Nobody ever paints the ceilings of their buildings right? Because it’s practically impossible to see them from any angle on your table. So providing the battery pack is low profile, it should never be seen.

To turn it on, just lift the roof and flick the switch. Batteries can be changed easily. It’s a good solution. The Lilypad runs at about £1.50 each, but they can be bought direct from China for about 50p if you are buying a few. Most people should be able to build them including the LED and battery for under £2.50 each. If you stick them onto the ceilings of your buildings with double sided tape, they are infinitely re-positionable - so you can easily play around with lighting effects on the fly.

I’m just working out the best diodes to use on them at the moment. I’ve just ordered some 5mm, warm-white, diffuse LED’s from Germany and I’m hoping they will have the right characteristics. If they work out, I’ll do a brief build guide. There will be soldering involved, but only soldering the legs of the LED directly onto the Lilypad …that’s about as easy as it gets really.

If you are allergic to soldering, it should be mentioned that Lilypad do a little kit that includes the battery holder, LED’s, a switch and a momentary button…

The intention is that they are all connected in parallel using conductive thread. Personally, I prefer the extra battery life from using just 1 LED per battery, but it is an option and their own LED’s are very neat.

[CoopsMinis]

A bit more about LED’s…

So what is the difference between a 5mm LED and a 3mm LED? Well not much in electronic terms. The internals are the same and the light output is the same (assuming they are built the same). The difference is just the plastic optic that houses them. But that does make a difference to what you see. The larger LED’s have a larger optic …obviously. The effect is that they throw more light in an even, all around pattern. The smaller LED’s are more ‘out-of’the’front’ focussed. It definitely has an effect on how the light is cast around, with the larger 5mm LED’s casting a nicer, more even light with more natural shadows. The downside is that 5mm LED’s are huge in terms of scale. So use 3mm LED’s (or smaller) if you are actually going to see the LED bulb directly, but if the bulb will be hidden, either in a recess or some kind of housing or lamp shade, then 5mm will give better results. So basically use 5mm unless aesthetics, scale or space prohibit it.

LED’s are also polar, in that they have a + and a - and must be connected correctly to work. The easiest way of working out which leg is which, is just to look at how long they are. The longer leg is always the +ve. But what if the legs have been clipped? Well if you can see inside the bulb, you can still tell. The internals of an LED look like this…

The leadframe inside has an anvil side and a post side. They look like little flags. The post side is always the smaller of the two and is always the +ve.

Alternatively, just connect em to a 3 volt power supply. If it works, you’ve got it right, if it doesnt, you havent.

I cant talk about LED’s and circuits without talking about Ohms law. Click to expand if you are really interested, or just ignore this bit…

Summary

If you really, really want to add a resistor in your circuit to properly balance it, then working out the correct resistor value is pretty simple. You need to know 3 things. Your input voltage from your power source (3 volts from the battery), the nominal or frontline voltage of the LED (varies usually from 1.8 to 3.6 volts) and the current draw …typically 20 mA, but can be lower on weak LED’s and much higher on very bright LED’s.

Ohm’s law formula. The resistor’s current I in amps (A) is equal to the resistor’s voltage V in volts (V) divided by the resistance R in ohms (Ω): V is the voltage drop of the resistor, measured in Volts (V).

Sounds complicated, but working out the right resistor is dead simple. As an example, lets assume we have 3 volts from our battery and an LED that runs on 2 volts and 20 mA.

3 (volts from the battery) - 2 (volts from the LED) = 1 (volt excess in the circuit)

To balance this…

1 (volt excess) divided by 0.02 (Amps …same as 20mA) = 50 (Ohms resistance).

To balance that circuit we need to put a 50Ohm resistor somewhere in the circuit.

So what if we have a 3 volt battery driving a 1.6 volt, 60mA LED?

3 - 1.6 = 1.4 (excess voltage)
1.4 / 0.06 = 23.33 Ohms (resistor required).

Alternatively, if you are super lazy, just stick a 100 Ohm resistor in all of em. Having too high a resistor value isnt a problem. Your LED might be fractionally dimmer than it could be otherwise, but you wont notice.

If you are really, really lazy like me, just ignore it altogether. You can use resistors if you want, I very much doubt I will use them. I’m not building satellites here.

Resistors only really become necessary (for our purposes) if you are running batteries pushing 4.5 volts or more or have multiple LED’s in a circuit. But just running 1x LED directly from 1x 3volt power supply, you dont need em.

[CoopsMinis]

Next up, diffuse versus clear?

This is actually a lot more interesting than all that dry stuff above. It makes a real difference. LEDs have this internal structure that gets ‘projected’ out of the lens on the front and it casts all sorts of odd shadows and artefacts. Not great for our purposes. In addition, they are designed with the lens on the front to throw most of the light straight out of the front …again, not idea if what you want is to illuminate and area or miniature room. But you can get diffuse LEDs. They are essentially the same but the plastic optic is clouded and refracted.

The two LEDs below are exacly the same, both 2 volt, 20mA, yellow flickering LED’s, except the one on the right is diffuse, the one on the left is standard, clear…

You can see here the difference in light output between them…

The diffuse LED has an all around illumination with smooth transitions from the hotspot to the shadow.

I think you’ll agree it’s pretty obvious the diffuse LED is miles better for our purposes.

OK, that about does it for the technical stuff, now just to get on and build them. If you have read this far, well done. Sorry there is no badge, there probably should be.

It’s just about making things now, I promise.

[Info_Overload]

I think I’ve seen people on YouTube lightly sand the standard LEDs to improve the diffusion, although that might be where they had either ran out of diffuse ones or they were just unavailable

[CoopsMinis]

@Info_Overload

I think I’ve seen people on YouTube lightly sand the standard LEDs to improve the diffusion

Yeah, you can do that, it’s just plastic. You can also spray them with a lacquer …or even paint them with a glaze. The main point is that the standard clear LED’s are very front focussed, which is worse the smaller they are and they tend to be full of shadows and artefacts unless you’ve done something to diffuse them. Easiest thing is just to buy the diffuse ones, they cost the same.

[Info_Overload]

@CoopsMinis

Easiest thing is just to buy the diffuse ones

Thanks

[Alaiteir]

That’s really useful info to know, especially the comparison between clear and diffuse!

[CoopsMinis]

Ok as promised, moving on to actually building stuff.

I mentioned a prototype Tilley/Hurricane lamp/ Well v1.0 got binned. It was based around a clear LED and most of the light was going up and what little spill was going all around, was casting some weird shadows full of lines and artefact. So I made v2.0 around a diffuse LED instead. I installed the lantern into a bit of scatter I was assembling. Remember my complaint about tea lights? Well my intention here was to have no suggestion at all of any battery or electronics sitting under the lamp…

My feeling here is that if it isnt at least reasonably convincing, it’s just not worth doing. You can be the judge of whether or not you think this works.

The other issue is whether or not it actually creates or adds atmosphere. If it doesnt, again it’s not worth doing.

I did a couple of quick vids, one in broad daylight and one just now in the dark to evaluate the light output…

Daylight

Night time

What do you guys think about the colour of the LED? It’s not super bright but remember you are looking dowen onto an LED. If it’s too bright it will be a huge distraction. It’s a question of getting it just right. Also there will be a ‘hat’ on the lamp when finished.

[Info_Overload]

That looks great, I think with the hat on it’ll be bang on
The colour works for me, it’s towards the yellow end of what I’ve seen of hurricane lanterns but very much within the range! It’s not super bright but it shouldn’t be. There’s no way a lantern should light up the whole table

[CoopsMinis]

Yeah, you can get ‘warm-white’ which isb probably a more accurate representation, but that is what I’m using for interior/electric light. It’s brighter and more natural. But I dont think I want brighter on this. I dont want to be staring at retina burning, epilepsy inducing LED bulbs all night long. For me the brightness is about right. It’s the colour I’m unsure of, though there arent many options really. It is a little too yellow, though it does show up well in daylight ironically …better than pure white.

[Info_Overload]

Warm white, might be more accurate. But it’s accurate for most electric lights too. I think the lanterns should be slightly more yellowy than electrics. Short of glazing yellow onto the lanterns I don’t see any way around it. And yellow is thematically appropriate even if it isn’t that accurate.
I like my terrain to be kinda accurate but sometimes you have to just say enough
And no one wants to game on an eye searingly bright table

[gallowsCalibrator]

Any advice for stringing together? I have a project that is running seven in a row and only have room for a single power source. Is there a way to run it off a coin cell? Does each light need a resistor?

[CoopsMinis]

It’s possible if you wire em in parallel. But it means your battery life will drop through the floor …probably about half an hour …and that is a lot of LED’s on one coin cell. I’m not sure the cell can sustain the current draw …you’d be right around 140mA which is pushing it, so you’d probably see dimming of the LED’s quite quickly. Technically each LED wired in parallel forms it’s own circuit and should have it’s own resistor. You dont actually NEED them with coin cells, but you might get better performance if you put one in …alternatively, just use white LED’s which have a front-line voltage of 3V and your need for a resistor will be 0. It’s doable, but whether or not the results will be satisfactory would require some experiment I think.

What is it that you are doing that needs all of those if you dont mind me asking? Have you thought about splitting the light from one LED with fibreoptics? Alternatively, do you have room for a pair of AA cells? That would be the way to go. If you are not up for the soldering, you can buy pre-wired LED’s with resistors already on them.

With regard to whether or not you need one resistor or a resistor for each LED, you can do either, like this…

or like this…

If are going to use just one, then you need to remember to change from 0.02 Amps as the current draw, to 0.14 Amps (the sume of all 7 LED’s) in your Ohms law calculation, which is why the resistor value is lower when useing just one (it’s actually 7.14 Ohms in the above example, but no such resistor exists so you just use the next highest which is 10).

[CoopsMinis]

Further to the above question about running multiple LED’s from a single cr2032…

I’ve been doing some reading and the consensus is pretty unanimous. The cr2032 cell is a very reliable battery, capable of holding it’s charge for many years and delivering constant performance. But… this is in relation to ultra-low current draw applications. Certain micro-electronics, digital watches and the like. Applications where the current draw is typically measured in microamps, rather than milliamps.

The issue with these batteries is that when you increase the current load on them, it dramatically impacts on their capacity. If we look at the Panasonic data sheet for the battery, we can see a quoted capacity of 220 mAh. That should power a 10 mA device for 22 hours for example. But that capacity is conditional providing the constant current draw of the device is at or below 0.2 microamps. That is 100x lower than the 20 miliamps of just one LED.

Clearly the battery will light up seven LED’s as in the pic above, the problem is they wont stay lit for long. With such a large current draw (140 miliamps) the internal resistance of the battery rises and it starts to operate in burst/rest cycles. You could run all seven LEDs for a few minutes, then they would dim and go out. Turn them off, the battery recovers and it can go again for a little while. Kind of like being over-encumbered.

It seems like these batteries cap out as about 40mA draw before they start to need rest cycles. That is just 2 LED’s.

As mentioned earlier running the battery in this way, has a devastating impact on the capacity. In fact from what I’ve read, running just one 20 mA LED constantly, can reduce that 220mAh capacity by as much as 50%. That scales, so running seven LED’s at 140 mAH and it’ll work in pulses, but you’ll basically destroy the battery in short order.

I’ve got some batteries coming and when they arrive, I’ll sacrifice a couple to runtime tests with 1, 2 and 3 LED’s attached. I strongly suspect anything more than 1 LED per battery will be impractical …and I also suspect it wont be possible to run anything more than 2 LED’s continuously for any length of time, without significant voltage drop and dimming of the LED’s.

Certainly for running seven LED’s, it’s just not going to work. They will light up for a few minutes, but they wont last and you’ll kill the battery. If you need to run that many off one power cell, then you need a power cell that doesn’t suffer this internal resistance problem. Perhaps a cell-phone battery? The obvious easy solution, would be AA’s or AAA’s.

[gallowsCalibrator]

I have to admit the project isn’t Fallout related, but this has been the best and easiest to understand tutorial I’ve come across.

I’m trying to get a light into each leg, the center orb and each array on top of the Storm Strider. I’ve cast clear resin copies of the model so they will shine through with a Blue Flicker led. Found here https://shop.evilmadscientist.com/productsmenu/partsmenu/796-blue3diffflicker

I could maybe fit as many as four or five coin cells into the base which never occurred to me till now honestly. Would splitting it up to two LEDs per coin cell work?

[CoopsMinis]

@gallowsCalibrator

Found here https://shop.evilmadscientist.com/productsmenu/partsmenu/796-blue3diffflicker

Would splitting it up to two LEDs per coin cell work?

It’s not the number of LED’s that matters, it’s the total current draw. Most LED’s are 20mA, so x2 standard LED’s draws 40mA’s. Those LED’s are 30mA, so 2 of those will be drawing 60mA’s. The same as 3x regular LED’s. You might get them to run but I dont think they will run very satisfactorily. You’d have to test it first. On the plus side, I have no doubt the sellers claim that they are ‘ultra bright’ will be quite true. With that current draw i would expect nothing less.

Personally, I dont think coin cells are the right solution for what you are doing. I mentioned it earlier, but have you thought of cell phone batteries? You can get them in all sorts of shapes and sizes but usually very thin, they are usually around 3.7 volts, a decent capacity (often 2000mAh) and are happy to deliver high current, they are cheap, especially on ebay and they are rechargeable. One battery will drive those 7 LED’s without issue and you’ll get a good runtime. You will need a resistor on each LED though. A voltage discrepancy between the LED and battery is a short circuit and due to the high current of a cell phone battery, there is a risk it will let the smoke out.

If I were you I would invest in a little breadboard starter kit like this…

The breadboard is the white brick in the middle. It’s just rows of holes that are connected electrically. You can just push-plug components like LED’s, resistors, capacitors or whatever into them, no soldering required. They are used to prototype circuits before committing to the solder stage. The set in the above pic was from ebay UK and was £1.49 with free shipping. I’m sure ebay US will have something similar.

In fact I would say breadboarding your idea first, would be essential for 2 main reasons.

Firstly, as mentioned you can prototype your circuit. You can test all your LED’s, make sure they work as advertised, make sure your circuit works, make sure the resistors work and test various switches and battery options. You can leave it running and check runtime. All good things to know before committing the circuit to your expensive model.

Secondly, you get to actually see the effect running. This is important because as I’ve discovered, you often dont like your initial choices. Most recently, I’ve disco9vered that flickering LED’s irritate me to death. Something I only found out after letting my prototype run for a while next to me. At first I thought it was cool, but after 10 minutes the flickering was annoying me so much I ripped the leads off the battery. I’ll be using standard LED’s for my lanterns from now on. I’m not saying you will feel the same, but those LED’s are going to be extremely bright and whether or not you can live with staring at that retina searing, epilepsy inducing flicker for a couple of hours, is worth finding out before you build em into your model.

[gallowsCalibrator]

Thank you so much for the advice! I’ve been scratching my head on this project for over six months and I finally feel like I can move forward.

Last question, you mention cell phone batteries? Can you post a quick example of what you had in mind? I’m not sure how that would work or how they would get recharged if it’s just the battery? Im prolly just over thinking something simple.